• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.4
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• pp.345-358
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• 2018

The high altitude scientific balloon has been used for decades in advanced aerospace countries such as United States, France, and Japan to carry out various research objectives. Since the initial cost for development and operation is enormous, it has been conducted by national research institutes. Recently, the advent of open source software/hardware ecosystems with low-cost yet high-performance have lowered barriers to enter into scientific balloon research and development. In this study, a zero pressure balloon prototype was designed considering the cost, usability, compatibility, and development period by using commercial off the shelf (COTS) items. In addition, the flight operation experience was accumulated through eight times of the flight tests, and operational reliability of the balloon system was verified. Finally, the foundation for the operation of the large zero pressure balloon was established.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.32-36
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• 2016

Test equipment was designed and manufactured to evaluate thermal reaction characteristic of internal insulators of solid rocket motor. Test is allowed up to chamber pressure 2,500 psi, burn-time 100 s. A cross section of test sample part is quadrature, and various test samples can be comparable at the same time. Inner temperature of test sample can be measured by thermocouples during burning. Test was executed in condition of efficient average chamber pressure 1,000 psi, efficient burn-time 10 s and safety of equipment was confirmed. Basic data for understanding thermal characteristics of internal insulator, that is, pressure-time curve, temperature-time curve in the test sample, and thermal destruction thickness of test sample was gained successfully.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.473-479
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• 2019

This study applied SGM (Semi Global Matching) to generate DSM (Digital Surface Model) using WorldView-1 high-resolution satellite stereo pair in Terrassa, Spain provided by ISPRS (International Society for Photogrammetry and Remote Sensing). The SGM is an image matching algorithm that performs the computation of the matching cost for the stereo pair in multi-paths and aggregates the computed costs sequentially. This method finally calculates the disparity corresponding to the minimum (or maximum) value of the aggregation cost. The cost was applied to MI (Mutual Information), NCC (Normalized Cross-Correlation), and CT (Census Transform) in order to the SGM. The accuracy and performance of the outline representation result in DSM by each cost are presented. Based on the images used and the subject area, the accuracy of the CT cost results was the highest, and the outline representation was also most clearly depicted. In addition, while the SGM method represented more detailed outlines than the existing software, many errors occurred in the water area.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.46-52
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• 2006

We report on a high performance 94 GHz MMIC resistive mixer using 70-nm metamorphic high electron mobility transistor (MHEMT) and micro-machined W-band ring coupler. A novel 3-dimensional structure of resistive mixer was proposed in this work, and the ring coupler with the surface micro-machined dielectric-supported air-gap microstrip line (DAMLs) structure was used for high LO-RF isolation. The fabricated mixer showed an excellent LO-RF isolation of -29.3 dB and a low conversion loss of 8.9 dB at 94 GHz. To our knowledge, compared to previously reported W-band mixers, the proposed MHEMT-based resistive mixer using micro-machined ring coupler has shown superior LO-RF isolation as well as similar conversion loss.

• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.181-185
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• 2005

Lithium cobalt oxide thin film cathode, having thickness of $2.9{\mu}m$ with area of $4cm^2$, was deposited on platinum patterned alumina substrate by radio frequency magnetron sputtering. Li/Co molar ratio, which is an important factor for battery performance, was measured as a function of argon working pressure and applied R.F. power. Constant current charge and discharge performances were characterized with high rate discharge and cycling behavior. Using AC impedance analysis, internal resistance of the thin film battery was measured and simulated by proposed equivalent circuit model.

• Korean Journal of Construction Engineering and Management
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• v.1 no.3 s.3
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• pp.101-107
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• 2000

On 1 July, 2000, the Ministry of Construction and Transportation announced the Earned Value Management System(EVMS) will be applied in public sector soon. However the arguments over the EVMS applied to our unique construction environment still exist and create strong concerns and worries among some experts it would be another mistakes proposed by the government. We do know the EVMS comes from C/SCSC which was first released by the United States Department of Defense in December 1967, and proved very powerful and efficient project management tool from a lot of practices. Although it is an excellent tool, we can not ignore our many experienced failures appling foreign system due to the differences of construction culture and law between the Korean and US construction industries. The purpose of the EVMS's success in Korea, therefore, this paper tests and proves the EVMS's adaptability and credibility to our construction environment by EAC model, that is one of the most important functions in the EVMS, using very scare EV data of the Korean construction projects.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.246-252
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• 2013

This paper presents method to suppress signal interference by using the filter in the RF output stage of the radiation equipment as a way to avoid interference between the RF(Radio Frequency) equipment mounted on aircraft. Especially filter design to suppress harmonics of the radiation equipment and testing method to verify the filter's performance is presented. Filter was installed at RF output stage of U/VHF radio in order to prevent interference between U/VHF(Ultra/Very High Frequency) radio and data link system. Filter design and testing method in this paper will be able to give help in the design of aircraft equipments as a tool that can be used to establish measures for problem of interference in the aircraft.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.185-193
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• 2013

The plume infrared signature effects at various flight conditions of aircraft were investigated for the purpose of reducing infrared signature level. The nozzle of a virtual subsonic unmanned combat aerial vehicle was designed through a performance analysis. Nozzle and associated plume flowfields were first analyzed using a density-based CFD code and plume IR signature was then calculated on the basis of the narrow-band model. Finally, qualitative information for the plume infrared signature characteristics was obtained through the analysis of the IR signature effects at various flight conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.6
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• pp.463-472
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• 2017

Inertial Navigation System Alignment is the process to determine direction cosine matrix which is the transformation matrix between the INS body frame and navigation frame. INS initial position value is necessary to INS attitude calculation, so that user should wait until he get such value to start the INS alignment. To remove the waiting time, we propose an alignment algorithm that immediately starts after the INS power on by using pseudo initial position input and then is completed with attitude error compensation by entering true position later. We analyse effect of INS sensor error on attitude in process of time and verify the performance and usefulness of the close-loop alignment algorithm which corrects attitude error from the change of initial position.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.117-126
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• 2009

Various dimensions of watershed structural/non-structural planning can be applied in comprehensive flood mitigation plan in a river basin. Especially structural counterplans have very broad and diverse nature as flood control facilities. It is not easy to find the optimum alternative to maximize the ability of a basin to reduce flood risk using a combination of structural counterplans. In addition, there is no standard for evaluating the performance of structural counterplans and for selecting optimal combination of them. This study focused on how to select the best alternative of a comprehensive watershed structural plan from various flood defense alternative candidates. By introducing an analytic hierarchy process, we would like to show how we decide the best alternative using standard worksheets developed in this study for economics and policy evaluation, and Expert Choice 11.5, which calculates weights for evaluation items. Based on the results from this study, we would like to suggest the best practice of a standardized watershed plan for flood protection.